57 results about "Hydrogen safety" patented technology

An apparatus and process for measuring the concentration of hydrogen gas being transferred through a nozzle from a source container to a destination container and for providing an alert and / or taking action where hydrogen gas leaks may create an unsafe condition. The invention can accurately and reproducibly respond to and measure the absolute hydrogen gas concentration within the nozzle housing using hydrogen gas sensors that are selective only to hydrogen, which do not require the presence of oxygen to operate and which do not saturate when hydrogen safety levels are reached. These sensors are positioned inside the nozzle housing to allow for the direct and immediate knowledge of the presence of hydrogen gas that cannot be safely determined by other means. An apparatus and process for detecting leaks of liquid hydrogen through a nozzle during transfer of liquid hydrogen from a source container to a destination container are also discussed.

The invention relates to a method for controlling feeding fuel to the inlet pipe of hydrogen motor and relative device, which can apply variable combustion engine with hydrogen fuel and it can apply electric control on the hydrogen ejection time and ejection period. The invention comprises a group of sensors to supply the information of hydrogen feeding system and the motor; a group of valves and pipeline to supply hydrogen resource; a electric control unit as the control center of said device; a hydrogen ejection system formed by a hydrogen stable-pressure rail, a hydrogen ejection valve, and hydrogen guide nozzle for guiding the hydrogen ejected from hydrogen ejection valve to nearest inlet valve; a electric air-saving gate on the inlet pipe of motor, a waste gas recycle valve between the inlet pipe and outlet pipe; and a hydrogen safety release valve on the crank box of motor. The invention ejects the hydrogen at the position which is nearest to the motor inlet valve into burning room, to reduce the backfire possibility of inlet pipe, reduce the discharge of NOx and control early-burning.

A safeguard with alarm function for high-pressure H2 container is composed of anti-impact unit at both end of said high-pressure H2 container, a safety valve able to be automatically opened when H2 pressure is too high, a high-safety fuse able to be fused when ambient temp is too high (fire accident for example) for releasing H2, and a pressure sensor for detecting the leakage of H2.

The invention relates to a hydrogen safety system of a fuel cell engine, which comprises a hydrogen pressure reduction protecting device. The hydrogen pressure relief protecting device is arranged between a disconnecting valve and a pressure maintaining valve; the hydrogen pressure relief protecting device comprises an ejector pump, a baffle plate, a spring, a piston and a pressure difference transducer; the baffle plate, the spring and the piston are arranged in a channel at the lower end of the ejector pump; the baffle plate is connected with the piston through the spring; the outlet of the channel at the lower end of the ejector pump is connected with the outlet of a channel at the right end of the ejector pump through a pipeline to ensure that the pressure of the lower surface of the piston is identical with that of the outlet position on the right side of the ejector pump; the baffle plate is provided with an air hole to ensure that the pressure of the upper surface of the piston is identical with that of the upper part of the baffle plate; a pressure difference is generated between the upper surface and the lower surface of the piston; the pressure difference or the deformation of the spring is transmitted to a controller through a transducer; the controller can control the opening and the closing of the disconnecting valve; when the hydrogen rate exceeds the maximum allowable value, the disconnecting valve is driven to automatically close, and the hydrogen source is cut off. Compared with the prior art, the invention has the advantages of simple structure, safety,reliability, and the like.

The invention relates to an encapsulation method of a galvanic pile module of a fuel cell, which comprises the following steps that: firstly, an integral galvanic pile is arranged in an encapsulation box from the rear end, eight fixed blocks on the galvanic pile are connected by bolts and software damping linings are arranged between fixed pins and the encapsulation box; secondly, on a back cover plate, a 1 millimeter white tetrafluoro pad is horizontally placed on a hydrogen joint, a 2 millimeter silica gel gasket is horizontally placed on a stainless steel joint, the white tetrafluoro pad and the silica gel gasket are stuck by fast-curing adhesives, and after curing, the back cover plate and the encapsulation box are fixed by eight M5-10 flange face screws and a red gasket; and finally, the galvanic pile module is arranged vertically, the back cover plate is downwards, and a front cover plate and the encapsulation box are fixed by the eight M5-10 flange face screws and the red gasket, so that the encapsulation of a galvanic pile module structure is completed. In the encapsulation method, components and parts in the integrated structure of the galvanic pile module of the fuel cell are integrated step by step; and the design that the fixed pins of the galvanic pile are connected with the encapsulation box is adopted, so that the galvanic pile module of the fuel cell has the functions of water prevention, dust prevention, seismic resistance, electric insulation, hydrogen safety protection, heat insulation and the like.

A hydrogen management system for a fuel cell vehicle includes a hydrogen control unit (HCU), a vehicle-mounted hydrogen detection and control module and a hydrogen safety module, the hydrogen controlunit (HCU) is used for managing the on-board hydrogen system, hydrogen safety detection and alarm for the whole vehicle, receiving a control command of a fuel cell control unit (FCU) and sending a hydrogen system detection signal to the FCU, The on-board hydrogen detection and control module comprises a hydrogen cylinder safety detection, a bottle mouth valve control and a pressure regulating system detection, wherein hydrogen in the hydrogen cylinder is decompressed by a pressure reducing valve and sent to a fuel cell stack, and the hydrogen safety module is used for hydrogen leakage detection of the whole vehicle. The fuel cell automobile hydrogen management system of the invention has clear interface with the fuel cell system and the whole vehicle control and the instrument system, realizes the unified collection and processing of the vehicle-mounted hydrogen-related signals, is safe and reliable, and is suitable for popularization and application.

The invention discloses an optical fiber hydrogen detecting device based on light heating. The device is characterized by consisting of a sensing light source (1), an optical fiber coupler (6), an optical circulator (7) and a sensing probe (8) which are connected in sequence, and a heating light source (2), an electronic control unit (3), a computer (4) and a spectrometer (5) which are connected in sequence, wherein the heating light source (2) and the spectrometer (5) are connected with the optical fiber coupler (6) and the optical circulator (7), respectively. The optical fiber hydrogen detecting device has the advantages of being capable of ensuring the sensitivity of the sensing probe in different atmosphere environments, being good in temperature resistance, humidity resistance and resistance to light-intensity variation interference in an optical fiber, being high in practicability, having a compensation function, accurately measuring the hydrogen concentration and having broad application prospect in hydrogen safety monitoring in the fields of energy sources, chemical engineering and the like in China.

The invention discloses a hydrogen safety control system and method for a hydrogen fuel cell vehicle. The hydrogen safety control system of the hydrogen fuel cell automobile comprises a hydrogen supply system controller, and a hydrogen bottle opening electromagnetic valve, an infrared module, a safety air bag controller, a whole automobile controller, a fuel cell controller, an automobile body controller and a combination instrument which are electrically connected with the hydrogen supply system controller. The hydrogen safety control method of the hydrogen fuel cell vehicle uses the hydrogensafety control system. The invention has the beneficial effects that when the hydrogen supply system controller detects that the hydrogen concentration inside or outside the vehicle is too high, theair bag controller detects collision, the fuel cell controller detects that a fuel cell system has serious faults, or the whole vehicle controller detects that a whole vehicle has electric leakage orhigh-voltage interlocking circuit faults, the hydrogen bottle opening electromagnetic valve can be immediately closed to ensure the safety of vehicles and users.

The invention discloses a modular hydrogen refueling station and a hydrogen sensitive tracer leakage monitoring system thereof. The hydrogen sensitive tracer leakage monitoring system comprises hydrogen sensitive detection adhesive tape, image acquisition devices, a control device and a safe leakage warning device, wherein the hydrogen sensitive detection adhesive tape is wrapped around the jointbetween hydrogen pipelines and the joint between valves and used for detecting hydrogen leakage by color changes; the image acquisition devices are used for shooting the images of the hydrogen sensitive detection adhesive tape and sending the shot images to the control device; the control device is used for judging the color changes of the hydrogen sensitive detection adhesive tape in the images,and when the color of the hydrogen sensitive detection adhesive tape changes, the control device determines that hydrogen leakage occurs and sends a fault signal to the safe leakage warning device; and the safe leakage warning device is in signal connection with the control device and used for giving out a hydrogen leakage alarm signal after receiving the fault signal. The hydrogen sensitive tracer leakage monitoring system can position hydrogen leakage points quickly and accurately and can provide a guarantee for the safety of hydrogen use.

The invention provides a hydrogen detection device of a fuel cell vehicle. The hydrogen detection device mainly comprises a controller, a basic framework, an alarm, a hydrogen safety monitoring sensor and a hydrogen emission detection sensor, wherein the basic framework has a height, length and width adjustable function, so that test demand on vehicles with different sizes is met; the device carries out hydrogen safety monitoring and hydrogen emission detection functions when being used for testing the fuel cell vehicle in a laboratory; and when hydrogen safety concentration exceeds standard, the device can give an alarm by virtue of the alarm. The hydrogen detection device provided by the invention can meet the hydrogen safety monitoring and hydrogen emission detection functions in a test scenario, required by the standard, according to the sizes of different fuel cell vehicles and is simple and reliable in structure and low in manufacturing cost.

The invention discloses an alarm system and method for detecting hydrogen leakage, and the system comprises a hydrogen production device which is used for producing hydrogen; a hydrogen compression device which is used for compressing and storing the hydrogen prepared by the hydrogen production device into a high-pressure hydrogen storage device; the high-pressure hydrogen storage device which isused for storing the hydrogen compressed by the hydrogen compression device and conveying the hydrogen to a hydrogen utilization device when the hydrogen utilization device needs to use the hydrogen;the hydrogen utilization device which is used for utilizing hydrogen; a hydrogen safety detection device which is used for detecting the hydrogen leakage condition and transmitting the detection information to an information processing and alarming device; and the information processing and alarming device which is used for processing the detection information and judging whether to give an alarmor not. According to the invention, the hydrogen leakage position can be simply, rapidly and effectively positioned, the alarm information can be conveniently and timely reported to the outside, the possibility that hydrogen leakage is gathered to reach an explosion limit is reduced, and major accidents can be effectively prevented.

The invention relates to the technical field of hydrogen energy automobiles, in particular to a hydrogen safety system of a fuel cell hydrogen energy automobile. The system comprises a hydrogen management system, a first hydrogen concentration sensor, a second hydrogen concentration sensor, a third hydrogen concentration sensor, a fourth hydrogen concentration sensor, a vehicle control unit, an automobile instrument, a hydrogen fuel cell system, a high-voltage distribution box, a power battery system, a driving motor system, a driving motor and an air conditioner compressor. Therefore, the hydrogen safety system of the hydrogen fuel cell automobile can accurately, quickly and sensitively send alarm information according to the hydrogen leakage level and control the whole automobile to takecorresponding protective measures, the safety of a driver and passengers is guaranteed, and the running safety performance of the automobile is remarkably improved.

The invention discloses a distributed power generation system and a control method thereof. The power generation system comprises a main control module, a methanol hydrogen production module, a protonexchange membrane fuel cell module, a system power supply module and a man-machine interaction module, the system further comprises an energy buffer module and a hydrogen safety module used for providing standby hydrogen. The methanol hydrogen production module, the proton exchange membrane fuel cell module, the system power supply module, the man-machine interaction module, the energy buffer module and the hydrogen safety module are all in control connection with the main control module; a load bus connected with a load is further included, and the load bus is in star connection with a direct-current conversion assembly of the proton exchange membrane fuel cell module and an electric energy management assembly of the energy buffer module; the load bus is provided with a voltage sensor and a current sensor, and is connected with the main control module. The system has the advantages of being reasonable in structural design and good in safety performance, and the method has the advantages of being small in power fluctuation, beneficial to improving power generation efficiency and the like.

The invention provides a fuel cell vehicle and a hydrogen safety control method, device and system thereof, and the method comprises the steps: detecting the pressure and the temperature of a hydrogenstorage bottle in real time, and determining the mass of hydrogen discharged by a hydrogen storage bottle in a set time according to the pressure and the temperature of the hydrogen storage bottle atdifferent moments and the volume of the hydrogen storage bottle; determining the hydrogen release rate of the hydrogen storage bottle according to the mass of the hydrogen released by the hydrogen storage bottle within the set time, the set time and the hydrogen density under the standard condition; and if the hydrogen storage bottle deflation rate is greater than the set deflation rate maximum value, controlling the hydrogen storage bottle to stop deflation. According to the invention, the temperature and the pressure of the hydrogen storage bottle can be detected by using the existing temperature sensor and pressure sensor on the fuel cell vehicle, the hydrogen leakage can be prevented without using an overflow valve, and the cost of a hydrogen system is reduced; meanwhile, the overflowvalve is not needed so that high-pressure pipeline joints are greatly reduced, pipeline leakage points are reduced, the safety of a hydrogen system is improved, and the safe operation of the fuel cell vehicle is ensured.

The invention provides a closed cabin system for the hydrogen safety test of a fuel cell vehicle. The closed cabin system comprises a closed cabin for parking a vehicle; and a gas exchange device anda test system capable of testing the hydrogen concentration are arranged inside the closed cabin and are connected with a control system. The closed cabin is provided with a sealing door for entranceor exit of a vehicle. With the provided closed cabin system, a problem of lack of a closed test device for simulating an actual parking space of a vehicle in the prior art is solved.

The invention discloses a hydrogen safety test system of a fuel cell vehicle. The hydrogen safety test system comprises a hydrogen storage device, a hydrogen conveying pipeline connected with the hydrogen storage device, a first pressure sensor, a flow control device, a hydrogen concentration detection module and a test pipeline, wherein the first pressure sensor and the flow control device are arranged on the hydrogen conveying pipeline; one end of the test pipeline is used for being connected with a hydrogen conveying pipeline, and the other end of the test pipeline is used for being fixed to a potential leakage point of the fuel cell vehicle; and the hydrogen concentration detection module comprises a plurality of hydrogen concentration sensors. The hydrogen safety test system of the fuel cell vehicle simulates the flowing and leakage of hydrogen in the operation process of the fuel cell vehicle, detects the concentration of hydrogen leaked from the potential leakage point under theset pressure and the set flow by utilizing the pressure sensor, the flow control device and the hydrogen concentration sensors, and obtains the leakage condition of the potential leakage point; and the hydrogen concentration sensors are reasonably arranged according to the leakage condition, the safety of the whole vehicle is improved, potential safety hazards are reduced, unnecessary hydrogen concentration sensors are prevented from being arranged, and the cost of the whole vehicle is reduced.

The invention discloses a dynamic hydrogen charging slow tensile test device for a metal bar-shaped sample. The device comprises an electrochemical hydrogen charging device, a liquid carrying table, the bar-shaped sample and a clamp. The bar-shaped sample penetrates through the liquid carrying table through the clamp and is fixed, and the electrochemical hydrogen charging device is connected withthe liquid carrying table. A scale distance section and an arc transition section of the bar-shaped sample are positioned in a columnar container, and the scale distance section is immersed in the electrolyte of the columnar container. The problems of hydrogen charging potential safety hazards, limited hydrogen charging content and hydrogen escape are solved. The device has the advantages of beingsimple in structure, easy and convenient to operate, accurate in experiment parameter, good in sealing performance and capable of keeping a complete sealed state and simulating actual working conditions to the maximum extent.

The invention discloses an integrated hydrogenation machine which comprises a hydrogenation pipeline arranged in a shell and a hydrogenation gun arranged outside the shell, the hydrogenation pipeline comprises a first hydrogenation pipe, a second hydrogenation pipe and a third hydrogenation pipe, and the two ends of each hydrogenation pipe are connected to a hydrogenation input pipe and a hydrogenation output pipe respectively. Each hydrogenation pipe is provided with a manual control valve, a hydrogenation pressure monitoring pipeline and a pneumatic control valve, each hydrogenation pressure monitoring pipeline is provided with a hydrogenation safety valve with a hydrogenation diffusion pipe, each pneumatic control valve is connected with an instrument gas branch pipe, and each instrument gas branch pipe is provided with an electric control valve. The electric control valve is in signal communication with a hydrogenation control module, and the instrument gas branch pipe is connected to an instrument gas input pipe. The design pressure of the three hydrogenation pipes is the same as the relief pressure of the safety valve. A cooler is arranged on the hydrogenation output pipe. The integrated hydrogenation machine has the advantages that the hydrogenation machine can be ensured to perform hydrogenation work all the time, and the hydrogenation machine is wide in application range and good in compatibility.

The invention discloses a hydrogen strong exhaust system and a hydrogen strong exhaust method. The hydrogen strong exhaust system comprises a hydrogen sensor arranged at a hydrogen accumulating point inside an automobile and a collector, wherein the collector is connected with a fan through a sealed pipeline, and the hydrogen sensor is used for measuring hydrogen concentration of the hydrogen accumulating point. When the hydrogen concentration exceeds a specified value, the fan is switched on, and the hydrogen passes through the fan from the collector, and is exhausted through an exhaust pipe. Due to the fact that a fuel battery automobile hydrogen strong exhaust system is added, hydrogen at the hydrogen accumulating point is exhausted in a forced mode, the exhausting mode is changed from a passive mode to an active mode, accumulation concentration of the hydrogen is reduced, and safety of usage of hydrogen is effectively ensured.

The invention discloses a distributed passive hydrogen safety protection system, comprising an active hydrogen concentration monitoring system and a passive hydrogen concentration control system. The passive hydrogen concentration control system comprises a housing, and an air entraining zone, a catalytic zone and an air guide zone which are successively distributed in the housing from down to top, wherein the air entraining zone employs an inner trapezoid design, and is used for entraining external hydrogen and air; the catalytic zone employs a Pt or Pd material as a catalyst, and is used for mixing hydrogen, air and catalysts to realize passive catalytic reaction; the air guide zone is used for discharging residual air after catalysis and generated steam. The active hydrogen concentration monitoring system is used for monitoring the concentration of hydrogen introduced into the air entraining zone, and controlling the amount of hydrogen entering the air entraining zone. In accidents of hydrogen leakage, hydrogen blast, etc., the distributed passive hydrogen safety protection system can automatically and passively perform hydrogen safety protection without artificial additional active control, not only greatly improve hydrogen place safety, but also meet different place demands on hydrogen safety protection.

The invention provides a novel mobile hydrogen monitoring and alarming device, which comprises a cross rod and a vertical rod, wherein the vertical rod is provided with a cross-shaped fixing block, and the cross-shaped fixing block can slide up and down on the surface of the vertical rod in a position lockable mode; and the cross rod penetrates through the cross-shaped fixing block in the horizontal direction, and the cross rod can slide left and right in the cross-shaped fixing block in a position lockable manner. The novel mobile hydrogen monitoring and alarm device can realize hydrogen safety monitoring for a hydrogen fuel cell automobile by using the cross rod, the vertical rod, a hydrogen sensor, a sound-light alarm and a wireless alarm transmitter in a cooperative manner, and has thecharacteristics of convenient movement, convenient and fast use and accurate test effect.

The invention discloses a device and a method for maintaining liquid level balance of an alkaline electrolysis system and inhibiting a blow-by risk. The method comprises the step of installing a safety device for inhibiting the blow-by risk on a U-shaped pipe between two gas-liquid separators in the alkaline electrolysis system. The mode for restraining the blow-by risk of the two gas-liquid separators in the alkaline electrolysis system through the safety device comprises at least one of slowing down the flowing speed of liquid in the U-shaped pipe, increasing the flowing path of the liquid in the U-shaped pipe and reducing the flow of the liquid in the U-shaped pipe passing through the safety device. According to the invention, when the electrolysis power is changed, the alkali liquor in the gas-liquid separator on one side can be effectively prevented from carrying hydrogen or oxygen to flow into the other side under the action of pressure, so that the blow-by risk caused by breaking the liquid level balance is avoided, and the safety problem under the condition of off-grid hydrogen production of the fluctuating renewable energy source is solved; and the off-grid hydrogen production safety performance of the alkaline electrolysis system is improved.

The invention discloses a passive hydrogen recombiner with a wind electricity conversion function and application thereof. The passive hydrogen recombiner comprises a hydrogen recombiner body, a wind electricity conversion module and an energy storage module, wherein the side wall of the upper part of the hydrogen recombiner body is provided with an opening, and the wind electricity conversion module is arranged at the opening; the energy storage module comprises a protective shell, a storage battery built in the protective shell, and an asbestine layer arranged between the inner wall of the protective shell and the storage battery for thermal insulation; the wind electricity conversion module is connected with the storage battery through a leading wire. According to the passive hydrogen recombiner provided by the invention, hydrogen can be removed, and electric energy can be produced for being used by other emergency equipment at the same time under an emergency condition, so the tension condition of emergency power energy under the emergency condition is relieved, and further, the kinetic energy of flue flow circulation is converted into electric power while a containment and hydrogen safety are guaranteed, and the comprehensive utilization of energy sources is realized, and the safety of the nuclear power containment is improved, which has an important meaning to nuclear power safety.

The invention discloses a hydrogen fuel supply control method of a fuel cell, the fuel cell and an automobile. In the hydrogen fuel supply control method provided by the invention, a hydrogen cylindervalve is controlled to be closed in advance in a shutdown process of a fuel cell, so that hydrogen in a pipeline is just consumed after shutdown is completed, and a pressure reducing valve and the front and rear ends of a hydrogen ejector are in a balanced state. By means of the method, the problem of mechanical fatigue of the pressure reducing valve and the ejector in the system parking period is effectively solved, the durability of the pressure reducing valve and the ejector is effectively improved, and then the purpose of prolonging the service life of the pressure reducing valve and theejector is achieved; the situation that high-pressure gas at the front end of the hydrogen ejector enters a hydrogen cavity of an electric pile when the hydrogen ejector leaks inwards during parking of the system to damage the two sides of the hydrogen space of the membrane electrode of the electric pile due to bearing large pressure difference can be prevented; and the system hydrogen safety problem caused by external leakage of the pipeline between the hydrogen injector and the hydrogen cylinder during parking of the system can be prevented.

The embodiment of the invention provides a hydrogen refueling station control method, and belongs to the field of a hydrogen refueling station. The method comprises the following steps that ambient temperature is detected; and a maximum hydrogen refueling rate of the hydrogen refueling station is controlled according to the ambient temperature, wherein the lower the ambient temperature is, the greater the maximum hydrogen refueling rate is. According to the hydrogen refueling station control method and device and the hydrogen refueling station, the hydrogen refueling capacity can be maximizedunder the condition that the hydrogen refueling safety is guaranteed.

The invention discloses a private garage hydrogen leakage simulation test device and test method, and belongs to the technical field of hydrogen safety utilization. The device comprises a garage system, a high-pressure hydrogen discharge system, a high-sensitivity hydrogen concentration sensor, a concentration sensor support system and a nozzle base system. The hydrogen leakage direction is controlled through a high-precision lifting table and a high-precision rotating table, and the size of the nozzle is adjusted through sprayers with different hole diameters. The device is suitable for testing the hydrogen concentration field after high-pressure hydrogen leakage at different angles, and the high-pressure hydrogen release angle is adjustable so that the hydrogen concentration distribution after high-pressure hydrogen leakage in a garage under different conditions is tested, and the danger is evaluated.

The invention relates to the technical field of hydrogen safety management, and provides an energy-saving hydrogen fuel automobile hydrogen concentration alarm sensor and an alarm method. The energy-saving hydrogen fuel automobile hydrogen concentration alarm sensor comprises a vehicle signal input end, a primary alarm circuit and a secondary alarm circuit, wherein the vehicle signal input end is electrically connected with the primary alarm circuit and the secondary alarm circuit, when the hydrogen concentration of the detection position is larger than a first preset value and smaller than a second preset value, the primary alarm circuit starts primary alarm, and when the hydrogen concentration of the detection position is larger than or equal to the second preset value, the secondary alarm circuit starts secondary alarm. The energy-saving hydrogen fuel automobile hydrogen concentration alarm sensor can be suitable for vehicle running scenes, energy consumption is basically zero under the condition that the hydrogen concentration is low, the requirement for static power consumption of the whole vehicle is well met, safety state detection of vehicle hydrogen safety can be achieved on the premise that energy is saved, and the sensor has the advantages of being simple in structure, high in reliability, high in stability, good in energy-saving performance and the like.

The invention discloses a hydrogen fuel cell car hydrogen safety device. A hydrogen fuel cell car comprises a VCU (5) and a hydrogen cylinder (1); an exhaust pipeline (3) is arranged on a hydrogen safety device and connected to the hydrogen cylinder (1); an electromagnetic valve (2) is arranged on the exhaust pipeline (3); and the electromagnetic valve (2) is connected with the VCU (5) through a signal wire. The invention further discloses an active hydrogen safety releasing method of the hydrogen fuel cell car hydrogen safety device. By using the technical scheme, hydrogen is actively exhausted when a danger is confirmed and the hydrogen needs to be exhausted by using a flame sensor, a temperature, a collision sensor and other safety detection sensors, and therefore, the hydrogen exhaustopportunity is optimal; the hydrogen use safety coefficient is increased, and the safety of personnel in a car and the integral loss minimization are guaranteed to a maximum limit.